Effect Of Clinical Depression Risk And Physical Activity Status On Markers Of Inflammation In Individuals From The MIDUS Study

PURPOSE: To assess the relationship between clinical depression risk and inflammation in individuals from the Mid-Life in the United States (MIDUS) study. METHODS: Individuals from MIDUS wave three in 2014 with mental health survey and biomarker data (N = 1255, Age = 57 ± 12 years) were included in this analysis. Center for Epidemiologic Studies Depression Scale (CES-D) scores were used to categorize individuals as at risk (≥ 16; CES-D+) or not at risk (< 16; CES-D-) for clinical depression. Individuals were classified as physically active or sedentary by self-reporting “Yes” or “No” when asked if they perform ≥20 minutes of any exercise or activity, three or more times per week. Blood was analyzed for serum levels of C-reactive protein (CRP), interleukin 6 (IL-6), IL-8, and tumor necrosis factor-α (TNF-α). Depression risk by activity status analyses of variance with least-squared difference pairwise comparisons were implemented for all dependent variables. RESULTS: Health markers for the sample were impaired (BMI = 29.8 ± 6.6; fasting blood glucose: 102.2 ± 28.4 mg/dL; total cholesterol: 186.6 ± 40.2 mg/dL). Data for CRP, IL-6, IL-8, and TNF-α for depression risk and activity categories can be seen in Table 1. Main effects of both depression risk and activity status were observed for CRP and IL-6 such that sedentary individuals and CES-D+ individuals had elevated CRP and IL-6 compared to active individuals and CES-D- individuals, respectively. An interaction was present for IL-8 such that IL-8 was elevated in sedentary CES-D+ individuals compared to all other groups. No significant differences in TNF-α were observed among groups. CONCLUSION: Sedentary individuals at risk for clinical depression exhibit heightened markers of resting inflammation. Many factors may moderate this relationship such as use of antidepressant medication, alternative treatments for mental health conditions, and various general health markers, all of which should be explored in future analyses. - Means of CRP, IL-6, IL-8 and TNF-α among active and sedentary CES-D+ or CES-D- individuals CRP (μg/mL) IL-6 (pg/mL) IL-8 (pg/mL) TNF-α (pg/mL) At Risk for Clinical Depression Active 3.44 ± 0.40 3.09 ± 0.25 13.98 ± 1.33 2.12 ± 0.08 Sedentary 5.96 ± 0.57*¥† 4.89 ± 0.36*¥† 18.51 ± 1.85*¥† 2.31 ± 0.11 Not at Risk for Clinical Depression Active 2.55 ± 0.17*† 2.72 ± 0.11† 14.42 ± 0.55 2.21 ± 0.03 Sedentary 3.60 ± 0.32 3.59 ± 0.20 13.48 ± 1.05 2.28 ± 0.06 Main Effect of Depression Risk F, p 17.311, < 0.001 11.421, < 0.001 3.182, 0.075 0.152, 0.697 ηp 2 0.014 0.009 0.003 0.001 Main Effect of Activity Status F, p 21.040, < 0.001 29.343, <0.001 1.953, 0.163 2.798, 0.095 ηp 2 0.017 0.023 0.002 0.003 Interaction F, p 3.564, 0.059 3.622, 0.057 4.526, 0.034 0.527, 0.468 ηp 2 0.003 0.003 0.004 0.002